RFID systems are used as information management systems for commodity management, electronic settlement, and the like. In an RFID system, a contactless communication is made between a reader/writer and an RFID tag to transfer predetermined information. An RFID tag includes an RFIC chip for storing predetermined information and processing predetermined radio signals, and an antenna for transmitting/receiving high-frequency signals. In commodity management, for example, RFID tags are attached to commodities to be managed.
Generally, RFID tags are attached to the surface of a commodity, but RFID tags may also be embedded in a commodity by injection molding, for example. For example, FIG. 22 is a schematic diagram showing a flow 55 of resin in injection molding with a conventional RFID tag 51. The RFID tag 51 is generally in the shape of a flat board and includes an RFIC chip on an antenna board. In injection molding with the RFID tag 51, molding resin 54 comes into contact with the tag and the flow of the injected resin may be blocked by the tag. As a result, molding resin 54 may not fully fill the inside of a mold 52, leaving some resin-absent cavities, or the pressure by resin may move the RFID tag, causing the misalignment of the RFID tag. In addition, since the RFID tag 51 is subjected to the flow of hot resin, the thermal loads accumulated in the RFID tag 51 may damage the RFIC chip in the RFID tag 51. Moreover, The possibility of the RFIC chip being damaged increases even more when the tag is inevitably disposed such that its large surface directly faces the flow of resin.
Patent Document 1: Japanese Patent Laid-open Publication No. 2007-133617.
To protect the RFIC chip from the heat of resin, the surface of the RFID tag should be covered with a heat-resistant laminated sheet to protect the tag from the heat in injection molding, as disclosed in Patent Document 1 (identified above), for example.
The heat-resistant sheet, however, may further hinder molding resin from going behind the tag, leaving some resin-absent cavities, or move the tag from a predetermined position. In addition, the heat-resistant sheet made of a certain material or having a certain thickness may impair the communication properties of the RFID tag.